The invention relates to a fuel injection system including a device for metering fuel into an exhaust system of an internal combustion engine, particularly a common rail Diesel engine, with a high pressure fuel line extending from the common rail to the exhaust system for injecting fuel into the exhaust system and to a method for metering the fuel into the exhaust system.
It is known to collect soot particles contained in the exhaust gas of diesel internal combustion engines in particle filters. To regenerate the particle filter, the soot which is trapped in the particle filter is oxidized by means of oxygen. The temperature of the particle filter required for oxidation can be attained with the aid of an oxidation catalytic converter which is positioned upstream. For this purpose, a metered quantity of fuel is additionally sprayed into the exhaust gas of the internal combustion engine upstream of the oxidation catalytic converter, in order to thereby generate the required temperature increase by means of a chemical reaction of the fuel in the oxidation catalytic converter.
The laid-open specification DE 102 51 686 A1 discloses a fuel injection system having a device for metering fuel into an exhaust system of an internal combustion engine.
The injection system is designed in the form of an accumulator injection system (common rail). The accumulator injection system has a fuel pump which feeds fuel from a fuel tank into an accumulator and stores said fuel under high pressure. Connected to the accumulator are injectors which spray fuel from the accumulator in each case into one combustion chamber of the internal combustion engine. The injection system has an injection valve via which fuel can be sprayed into the exhaust system. An injection nozzle and an actuator which controls the injection nozzle are combined in the injection valve, with the actuator being activated by a control unit. The fuel pump conducts fuel from the fuel tank to the injection valve. Arranged between the fuel pump and the injection valve is a check valve which, in an emergency, can block the fuel flow to the injection nozzle. Also provided is a fuel pressure sensor which can measure the pressure of the fuel upstream of the injection valve.
The regeneration of the particle filter takes place at low exhaust-gas and oxidation catalytic converter or particle filter temperatures by means of the injectors, which spray additional fuel into the combustion chambers of the internal combustion engine. At high exhaust-gas and oxidation catalytic converter or particle filter temperatures, fuel is sprayed by means of the injection valve into the exhaust system of the internal combustion engine. This is intended to ensure that, in all load and speed ranges of the internal combustion engine, the fuel injected for the regeneration of the particle filter can pass into a vaporized state before the fuel impinges on the oxidation catalytic converter or as the fuel impinges on the oxidation catalytic converter. A disadvantage here is that the spraying of fuel by means of the injectors adversely affects the thermodynamic efficiency of the internal combustion engine and the device for metering fuel into the exhaust system of the internal combustion engine is not suitable for ensuring effective regeneration of the particle filter at low exhaust-gas and oxidation catalytic converter or particle filter temperatures.
It is an object of the present invention to provide an injection system having a device for metering fuel injected into the exhaust gas for an efficient regeneration of the particle filter in all load and speed ranges of the internal combustion engine, so that additional injection of fuel into the combustion chambers is not necessary.